Cell Biology and Membrane Systems
The cell as an organized nonequilibrium system
Compartments and transport
Cells organize chemistry through membranes, organelles, vesicles, and the cytoskeleton. This compartmentalization allows incompatible reactions to coexist and supports directional transport, signaling specificity, and metabolic coupling.
Principle
Spatial organization is not decoration; it is a mechanism for control.
Membranes and trafficking
Lipids, proteins, and transport routes
Membrane composition influences fluidity, curvature, and signaling. Endocytosis, exocytosis, and vesicular sorting rely on coat proteins, SNAREs, motor proteins, and Rab GTPases. Membrane contact sites and organelle communication are active frontier areas.
Selected cellular structures
| Structure | Primary function |
|---|---|
| Endoplasmic reticulum | Protein folding and lipid synthesis |
| Golgi apparatus | Modification and sorting |
| Mitochondrion | Energy conversion and signaling |
| Lysosome | Macromolecule degradation |
Which organelle is central to ATP production in eukaryotic cells?
Mitochondria generate ATP primarily through oxidative phosphorylation.
Correct answer: Mitochondrion
What is one function of the lysosome?
Lysosomes use acidic hydrolases to break down proteins, lipids, nucleic acids, and carbohydrates.
Correct answer: Degradation of macromolecules
Cytoskeleton and cellular mechanics
Mechanics meets signaling
Actin, microtubules, and intermediate filaments support cell shape, intracellular transport, division, and mechanotransduction. Cellular forces can influence gene expression through nucleus-cytoskeleton coupling.
Which cytoskeletal polymer is most directly involved in mitotic spindle formation?
Microtubules form the mitotic spindle that segregates chromosomes.
Correct answer: Microtubules
Name one emerging mechanism of non-membrane compartmentalization.
Phase separation can create dynamic biomolecular condensates that organize reactions.
Correct answer: Liquid-liquid phase separation